/**
 * 深度优先遍历
 */
#include <iostream>
using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right)
        : val(x), left(left), right(right) {}
};

class Solution {
public:
    int maxDepth(TreeNode *root) {
        if (root == nullptr) {
            return 0;
        }
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};

int main() {
    TreeNode *root = new TreeNode(1);
    root->right = new TreeNode(2);
    root->right->left = new TreeNode(3);

    Solution s;
    cout << s.maxDepth(root) << endl;
    
    return 0;
}